Improvement in cathode ray tubes for color tv receivers having a post-acceleration grid electrode

ABSTRACT

A two part hermetically sealed glass envelope or ampoule in the form of a cathode ray tube wherein the two portions comprise a vision screen member and a cone member which are sealed along a plane containing a sheet of parallel metal wires acting as a control grid electrode. A network of parallel and equidistance grooves are formed along oppositely disposed portions of the edge of at least one of the two members. The grid wires are placed in respective grooves so as to maintain the wires in parallel equidistance relation to one another. The edges into which the grooves are formed are disposed in a common plane between the cone and vision screen members. The grooves may be arranged in either a chamfered portion of the edge, or the thicker portion of the edge of at least one of the members of the envelope.

United States Patent Bradu 5] March 6, 1973 IMPROVEMENT IN CATHODE RAY 3,166,396 1/1965 Miller et al. ..65/59 X TUBES FOR COLOR TV RECEIVERS 3,240,850 3/1966 Hess ..65/59 x 3,284,653 11/1966 De France et al. ....3l3/89 c flglsrDi 3,489,966 l/ 1970 Bradu et al. ..313/83 [75] Inventor: Georges M. Bradu, Nemours, Primary Examiner-Palmer C. DemeO Fran Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak [73] Assignee: Societe des [derreries Industrielles [57] ABSTRACT Reumes du Lomg, Pans, France A d l two part hermetically seale g ass envelope or am- [22] Flled' 1968 poule in the form of a cathode ray tube wherein the [21 App] 775,070 two portions comprise a vision screen member and a cone member which are sealed along a plane containing a sheet of parallel metal wires acting as a control [30] Aplhcatlon Pnomy Data grid electrode. A network of parallel and equidistance Nov. 9, 1967 France ..67127494 are famed along oppositely di$PSed of the edge of at least one of the two members. The 52 us. 01. ..313/85 s, 65/59, 313/283 grid wires are Placed in respective as to 51 1m. 01. ..HOlj 29/06, H01 j 31/20 maintain the wires in Parallel equidhmhce elation 58 Field of Search ..313/85 s 283 285 286- amther- The edges whih the grooves are 8 formed are disposed in a common plane between the cone and vision screen members. The grooves may be 56 f arranged in either a chamfered portion of the edge, or 1 Re erences Clted the thicker portion of the edge of at least one of the UNIT STATES PATENTS members of the envelope.

2,813,213 11/1957 Cramer et al ..313/78 7 Claims, 7 Drawing Figures 4' b V Tl.

IMPROVEMENT IN CATHODE RAY TUBES FOR COLOR TV RECEIVERS HAVING A POST- ACCELERATION GRID ELECTRODE This invention relates to an improvement in the production of cathode ray tubes provided with an inside grid of the post-acceleration type. More particularly, it involves a structure of ampoules for such tubes, provided for the reproduction of polychrome images.

There now exists a number of cathode ray tubes for color television, including a grid that performs a postacceleration function, arranged between the electronic guns and parallel luminescent bands, on the inside face of the vision screen. The wires of the grid are held parallel and at a very precisely predetermined distance from the luminescent bands.

According to one currently known method of preparing the grid, the metal wires which later on will constitute the grid are first stretched out on a metal framework outside the screen. A framework which is removable and massive, hence heavy, to support the mechanical stresses is placed upon the wires, so as to reduce or perhaps even entirely eliminate the eventual vibration of the wires which would disturb the quality of the polychrome information transmitted. A network of wires which are equidistant by a value suitable for the definition of the retransmitted image are thereby prepared.

The assembly, consisting of the wire network and the framework, is applied on the edge of the viewing screen, covered with a sealing layer of fusible glass or a vitrocrystalline substance. It is then sealed between the cone and the viewing screen in the course of a series of heating cycles necessary for making an effective and tight glass-metal seal. The dilatation residues resulting from these successive heat treatments are expressed by deformations in the framework, which are perfectly arbitrarily distributed and which impair the precision of the positioning of the grid wires by destroying the parallelism and/or equidistance of the wires.

Another element that acts in a rather uncontrollable fashion and in an unfavorable manner consists in the existence of relative displacements due to the difference between the dilatations of the metal framework and the glass, the dilatation curves of which are not superposed under the working conditions required. Now, it is essential that both parallelism and equidistance are achieved in the grid wires, so as to obtain an acceptable polychromatic image.

This invention is intended to prevent these inconveniences by means of a new structure for at least one of the two glass pieces constituting the ampoule. It is also intended to provide a method for mounting a sheet of stretched metal wires, in a cathode ray tube, which serve as a post-acceleration or post-focalization grid, using new means that guarantee the automatic equidance of the wires of the sheet.

According to the invention, following all of the techniques currently known in glass work, a network of parallel and equidistant grooves is made which matches the grid adapted for the vertical definition of the image. This network structure may be made over all or a portion of the thickness of the edge of one or another of the glass pieces (either the cone or vision screen) which constitute the enclosure.

The cathode tube, comprised of the two part glass ampoule, which is the object of this invention, then has in the sealing plane of the cone and the vision screen a sheet of wires, parallel to the sheet of luminescent bands. The positioning of the wires comprising the sheet is assured by their placement in a network of grooves as defined earlier, maintaining their immobilization and rigorous equidistance.

The above characteristics, as well as other secondary characteristics and the advantages resulting from the invention will emerge in greater detail in the specifications below wherein some particular ways of implementing this invention are described by way of indication to specified embodiments referenced in the attached drawing, wherein:

FIG. 1 is a schematic drawing of a longitudinal section of a cathode tube with post-focalizing grid;

FIG. 2 is a perspective and partial section view of one possible version of the invention, on a piece made of glass;

FIG. 2A shows a top view of the glass piece in FIG. 2;

FIG. 3 shows a view similar to that of FIG. 2, for another variation of this invention;

FIG. 3A shows a top view of the glass piece in FIG. 3;

FIG. 4 shows a view similar to that of FIG. 2, on another possible version;

FIG. 4A shows a top view of the glass piece in FIG. 4.

Referring back now to FIG. 1, a color television tube is illustrated consisting of a screen 1 and a cone 2, connected by a soldering line 3, on the level of their edges, which serves as a seal for a sheet of wires 4, acting as the post-focalizing grid. Vision screen 1 is represented, according to one form of the invention here, with an internal plane structure 5.'On this surface is arranged the trichromatic phosphorus bands n, v, b. The screen may have a circular geometry or a rectangular one with the corners rounded off. The front face can be flat or curved and the circumference of the screen may have a skirt of variable height. The characteristics of the invention are applicable to all possible structures of ampoule components.

In one known method of attaching the sheet of grid wires in soldering plane 3, the following steps are followed:

a. The plane of grid wires, stretched by the outside metal framework is applied against the set-up edges of the vision screen, parallel to the trichromatic luminescent bands. A belt of sealing material is deposited on the edge of the vision screen;

. the edge of the cone, likewise erected, is prepared with the same sealing material and joined to the edge of the vision screen, in order to make the two glass pieces one. These are the two glass pieces which will enclose the wire sheet between them; I

0. After the soldering, the wires are cut flush with the outside edge of the welding seam 3. Over the entire periphery of this scam, in other words, on the flush-cut wires, a line or belt of conducting material is applied which insures that the grid wires will have the same potential. A layer of ceramic-treatable glass is then also applied, which serves to strengthen the tightness of the seal.

Considering the successive heating cycles for each soldering operation, it can easily be understood that the metal frameworks used to extend or stretch the metal wire sheet are rather quickly warped and that precision in the positioning of the wires is upset by the dilation residues.

This is why the means permitting parallelism and equidistance in the wires are placed directly on the tube per se. The framework of the present invention only serves to provide mechanical support. In accordance with this invention, a network of grooves is placed along the edge of at least one of the glass pieces constituting the ampoule (either the vision screen and/or the cone) and over the grid. The wires stretched by the framework will automatically be placed into these grooves. It should be noted that the grooves can be placed over all or a portion of the edge of the glass piece considered here, depending upon the configuration adopted for that piece.

It is obvious that the distortions of the framework, which previously have impaired the equidistance and parallelism of the network elements, no longer have any repercussions on the positioning of these elements, because, during the subsequent heating cycles the grid wires, enclosed in sealing material, are guided and kept in place in the grooves.

The grooves which are intended to receive the grid wires can be made by an etching process through the use of an acid mixture on the desired zones along the edge of the glass piece. These zones may be defined either by the local removal of a wax which has earlier been deposited on the edge, or by means of insolation, via a mask, of a photo-sensitive material'covering the above mentioned edge of the glass piece.

By way of example, we can use the following acid mixture for liters of solution:

1.94 liters of 95% S0,,l-I

7.00 liters of 60% FH 1.06 liter water.

Instead of the etching method for forming the grooves, a diamond-stubbed saw or any other method employed in glass working may be utilized.

Several variations of this grooving process have been contemplated by the applicant, without any restrictions on the scope of the invention. In FIGS. 2 and 2A, for example, the outside circumferential edge of vision screen 1 has been bevelled along l'a and the upper face has been prepared and then grooved along l'b so as to receive the grid wires.

On FIGS. 3 and 3A, the upper face of the edge of the vision screen has been prepared after having first been bevelled along 1"a and grooved along 1"]; on the chamfer thus constituted.

On FIGS. 4 and 4A, the edge of the vision screen, which has first been prepared, was, on the one hand, notched with one step, over a portion of its width at l" a, and on the other hand it was grooved along 1" 'b. The material forming step 1 'a can be removed either along with the grooving operation, if the etching process is used, or before or after placing it etchant on' the grooves.

In this particular case, an etching process to form the grooves and a milling operation to form step 1" 'a may be used. This particular variation enables the use of two types of cones.

The presence of step 1 'a can be used in order to solder a thin-edge cone whose edge has been bent up, with essentially the same width as the step 1" 'a. The

soldering seam then extends in the groove, envelops the wire and seals the faces with respect to the screen and the cone. Grooving can also be provided on the edge of the cone so that the wires will be guided on the level of step 1" 'a by the grooving of the cone and on the level of the initial edge by the grooving of the vision screen.

A cone with thick edges, can also be used which itself has been cut in step-fashion, having a shape complementary to that of the edge of the vision screen. The soldering seam then extends in the groove in which there is placed the wire, where it envelops the wires and then connects the faces opposite the vision screen and the cone with each other. The same technique of double grooving, mentioned above, is still applicable here. The groove network on the edge of the cone is then made on the portion of the complementary edge of step 1" 'a. The alignment of the axes of the grooves of the two networks can be assured by centering pins or the like provided on the two glass pieces for the positioning of the masks used in the photoengraving process.

It must be noted that this groove network can also be placed in the edge of the cone only. It may nevertheless be worth while to make it preferably on the screen because we can thus very simply guarantee automatic parallelism between the grid wires and the trichromatic luminescent bands. In this arrangement one can also more easily and more precisely define the distance between the plane of the grid wires and the plane of the luminescent bands. To do this, it suffices to use centering pins for positioning the mask that serves to define the grooving pattern. These centering pins will be provided outside the glass piece, so that one can perform the operation of depositing the luminescent bands.

What is claimed is:

l. A cathode ray tube for a color TV receiver comprising;

a. a viewing screen portion,

b. a cone portion,

c. at least one of said portions having two identical sets of parallel, equidistant grooves in the peripheral edge at oppositely spaced locations on said peripheral edge with the grooves of one set being aligned with the grooves of the other set,

d. an internal control grid comprised of a plurality of equally spaced parallel wires, the ends of said wires being disposed in said aligned sets of grooves to maintain the equidistant parallelism of said wires, and

e. means sealing said portions along the peripheral edges of both portions in substantially a common plane and securing said wires in said grooves.

2. A cathode ray tube as set forth in claim 1 wherein said grooves are disposed in the major portion of the wall thickness of the peripheral edge of at least one of said portions forming the envelope parallel to said common plane.

3. A cathode ray tube as set forth in claim 1 wherein an external portion of the peripheral edge of at least one of said portions is chamfered, said grooves being located in said chamfered portion.

4. A cathode ray tube as set forth in claim 1 wherein an external portion of the peripheral edge of at least one of said portions is chamfered and said grooves being located within the remaining plane portion of said peripheral edge parallel to said common plane.

said portion in which the grooves are located is the viewing screen portion.

7. A cathode ray tube as set forth in claim 1 wherein the portion in which the grooves are located is the cone portion.' 

1. A cathode ray tube for a color TV receiver comprising; a. a viewing screen portion, b. a cone portion, c. at least one of said portions having two identical sets of parallel, equidistant grooves in the peripheral edge at oppositely spaced locations on said peripheral edge with the grooves of one set being aligned with the grooves of the other set, d. an internal control grid comprised of a plurality of equally spaced parallel wires, the ends of said wires being disposed in said aligned sets of grooves to maintain the equidistant parallelism of said wires, and e. means sealing said portions along the peripheral edges of both portions in substantially a common plane and securing said wires in said grooves.
 1. A cathode ray tube for a color TV receiver comprising; a. a viewing screen portion, b. a cone portion, c. at least one of said portions having two identical sets of parallel, equidistant grooves in the peripheral edge at oppositely spaced locations on said peripheral edge with the grooves of one set being aligned with the grooves of the other set, d. an internal control grid comprised of a plurality of equally spaced parallel wires, the ends of said wires being disposed in said aligned sets of grooves to maintain the equidistant parallelism of said wires, and e. means sealing said portions along the peripheral edges of both portions in substantially a common plane and securing said wires in said grooves.
 2. A cathode ray tube as set forth in claim 1 wherein said grooves are disposed in the major portion of the wall thickness of the peripheral edge of at least one of said portions forming the envelope parallel to said common plane.
 3. A cathode ray tube as set forth in claim 1 wherein an external portion of the peripheral edge of at least one of said portions is chamfered, said grooves being located in said chamfered portion.
 4. A cathode ray tube as set forth in claim 1 wherein an external portion of the peripheral edge of at least one of said portions is chamfered and said grooves being located within the remaining plane portion of said peripheral edge parallel to said common plane.
 5. A cathode ray tube as set forth in claim 1 further comprising means defining a circumferential notch in an external portion of the peripheral edge of at least one of said portions to form a step, said grooves being located within the remaining projecting portion of said peripheral edge.
 6. A cathode ray tube as set forth in claim 1 wherein said portion in which the grooves are located is the viewing screen portion. 